This invention is related to cleaning a wellbore of fill, and more particularly, to cleaning an oil/gas wellbore of substantial fill using coiled tubing.
Solutions exist to an analogous problem in a related field, the problem of cuttings beds in the field of coiled tubing drilling in deviated wells, a field employing different equipment in different circumstances. The solutions are similar but have important distinctions with regard to the instant invention. Some, though not all, practitioners when drilling with coiled tubing (CT) in deviated wells cleanout cutting beds that develop by a wiper trip. Cuttings in a deviated well periodically form beds under CT, uphole of the drilling, notwithstanding the efforts to circulate out all of the cuttings with the drilling fluid. Some practitioners periodically disturb and,entrain and circulate out their cuttings beds by dragging the bit and its assembly back uphole, while circulating. This bit wiper trip is a relatively short trip through a portion of the borehole and is interspersed, of course, with periods of drilling where more cuttings are created and are (largely) transported out by the circulation of the drilling fluid. The need for a wiper trip is determined by gauging when a cuttings bed is causing too much drag or friction on the coiled tubing such that it is difficult to lay weight on the bit.
The bit wiper trip typically does not comprise a full pulling out of the hole (xe2x80x9cPOOHxe2x80x9d) but rather for only 100 feet or so, progressively increasing as more hole is drilled. The trip length may increase as the hole gets deeper. POOH rates with the bit wiper trip are not known to be scientifically selected using computer modeling. This is not a workover situation that targets substantial cleaning of fill in one wiper trip. A bit and its assembly comprise a costly and elaborate downhole tool for a wiper trip.
Key distinctions between the instant invention and periodic bit wiper trips include, firstly, the use herein of a far less expensive jetting nozzle as compared to an expensive drilling bit, motor and associated assemblies, to disturb and entrain the fill. A second distinction is the use of rearward facing jets while POOH by the instant invention. A third key distinction is the engineered selection of pump rates and/or RIH rates and/or POOH rates, based on computer modeling, in order to target a cleanout of the hole in one trip.
In regard to the computer modeling of wells, in general, and further in regard to the modeling of cleanouts per se, it has been known in the art to model a solids/cuttings bed cleanout by modeling circulation in a deviated hole containing coiled tubing. To the inventors"" best knowledge, however, it has not been known to model two phase flow in these circumstances nor to model the effects of a dynamic wiper trip while jetting. In particular it has not been known to model a wiper trip involving POOH with a nozzle having uphole pointing jets.
Turning to the well cleanout industry in particular, one problem that has historically faced well owners and operators is the question of whether a well is clean in fact when, during a cleanout, the well is flowing clean with the workover coiled tubing (CT) at target depth (TD). A second problem: is that since many of the so-called xe2x80x9croutinexe2x80x9d cleanouts are not as simple as might be expected, the usual definition of xe2x80x9ccleanxe2x80x9d is likely to be set by local field experience and may not represent what can or should be achieved. A third problem has been determining the question of how clean is clean enough. An ineffective or incomplete well cleanout results in shorter production intervals between cleanouts and increased maintenance.
It costs more to re-do a job than to do it right the first time. The object of the instant invention is to ensure that owners/operators do not incur the costs of recleaning their wells for as long as possible, prolonging well production and maintaining wireline accessibility. A well that requires a cleanout every 12 months between poorly designed, incomplete jobs may last 24 months between properly designed cleanout jobs.
Unless a well is a vertical hole ( less than 35xc2x0 deviation) with a generously sized completion assembly and moderate bottom hole pressure, cleanout procedures according to conventional practices are likely to leave significant debris or fill in the hole. One further object of the instant invention is to offer a comprehensive engineered approach to CT cleanouts, targeted to substantially clean a hole of fill in one trip.
In one preferred embodiment the invention includes a method for cleaning fill from a borehole comprising disturbing particulate solids by running in hole, in typical cases through substantial fill, with a coiled tubing assembly while circulating at least one cleanout fluid through a nozzle having a jetting action directed downhole. This invention may include creating particulate entrainment by pulling out of hole while circulating at least one cleanout fluid through a nozzle having a jetting action directed uphole. The invention may include controlling at least one of 1) the pump rate of the cleanout fluid and/or 2) the coiled tubing assembly pull out rate such that substantially all particulate solids are maintained uphole of an end of the coiled tubing assembly during pull out. The invention may also include controlling the POOH rate so that equilibrium sand beds are established uphole of the jets, if or to the extent that such beds were not established during running in hole (RIH).
The invention can include in one embodiment a method for cleaning fill from a borehole in one wiper trip comprising jetting downhole, through a nozzle connected to coiled tubing, at least one cleanout fluid during at least a portion of running downhole. The invention can include jetting uphole through a nozzle connected to the coiled tubing at least one cleanout fluid during at least a portion of pulling out of hole. The invention can include pumping during at least a portion of pulling out of hole at least one cleanout fluid at a selected pump rate regime, pulling out of hole for at least a section of the borehole at a selected pulling rate regime, and substantially cleaning the borehole of fill. Preferably the invention includes high energy jetting downhole and low energy jetting uphole.
The invention can include a method for cleaning a borehole of fill comprising sweeping back at least one uphole directed jet connected to coiled tubing while pulling out of hole at a selected pulling rate regime. This invention can include pumping at least one cleanout fluid at a selected pump rate regime down the coiled tubing and out the at least one jet during at least a portion of pulling out of hole. The invention can also include selecting, by computer modeling, at least one of 1) pump rate regime and/or 2) pull out of hole rate regime such that one sweep substantially cleans the borehole of fill.
The invention can include a method for cleaning out a borehole of particulate matter comprising modeling a cleanout, taking into account a plurality of well parameters and a plurality of equipment parameters, to produce at least one running parameter regime predicted to clean to a given degree the borehole with one wiper trip of coiled tubing, the coiled tubing attached to at least one forward jet and one reverse jet. This invention can include cleaning the borehole to obtain the given degree of cleanout in one wiper trip with the coiled tubing while implementing at least one produced running parameter regime.
The invention can include apparatus for cleaning fill from a borehole in one wiper trip comprising a nozzle adapted to be attached to coiled tubing, the nozzle having at least one high-energy jet directed downhole, at least one low energy jet directed uphole and means for switching in the nozzle fluid flow from the at least one high energy jet to the at least one low energy jet.
The invention can include a method for cleaning fill from a borehole in one wiper trip comprising computer modeling of solids bed transport in a deviated borehole while pulling out of hole with coiled tubing according :to pulling out rate regime and while jetting uphole at least one cleanout fluid according to a cleanout fluid pump rate regime.
In preferred embodiments the invention includes tool design and methodology for coiled tubing in vertical, deviated, and horizontal wells. The invention includes running coiled tubing into the well while circulating water, gelled liquids or multiphase fluids using a nozzle.with a xe2x80x9chigh energyxe2x80x9d jetting action pointing forwards down the well to stir up the particulate solids and allow the coiled tubing to reach a target depth or bottom of the well. When the bottom or desired depth is reached, the invention includes reversing the jetting direction of the nozzle to point upward (up the wellbore) while circulating water, gelled liquids or multiphase fluids using a low energy vortex nozzle that will create a particle re-entrainment action to enhance agitation of the solids and then entrain the solids in suspension for transport out of the wellbore while pulling the coiled tubing out of the hole. The reverse jetting action along with a controlled pump rate and wiper trip speed can produce a solids transport action which cleans the hole completely by keeping the cuttings in front (upward) of the end of the coiled tubing in continuous agitation. The low energy nozzles have a low pressure drop which allows for higher flow rates which results in improved cleanout efficiency. This method and tool is more efficient than existing methods since the process may be limited to one pass or sweep with the option of resetting the tool for repeated cycles if problems are encountered.